1. Field of the Invention
This invention relates to a continuous medium printing apparatus which prints on a continuous medium such as continuous recording paper (continuous paper), for example, by electrophotography.
2. Description of the Related Art
Generally, a printing process station for a continuous paper printer (continuous medium printing apparatus) which adopts electrophotography includes a photosensitive drum (image forming drum) capable of forming a print image on continuous paper (which may be hereinafter referred to merely as paper) while rotating in a printing transporting direction of the continuous paper, and several apparatus (for example, a precharger, an exposure unit, a development unit, a transfer charger, an AC discharger, a cleaning unit, an LED discharger and so forth) disposed around the photosensitive drum for performing various processes such as charging, discharging, exposure, development and cleaning.
In order to load such continuous paper as described above into the continuous paper printer, an operator will first set a leading end of the continuous paper to a suitable position on a paper transport path and then render an automatic loading mechanism (automatic paper setting mechanism) operative. Consequently, the continuous paper is automatically loaded into the continuous paper printer and set to a printable state by the automatic loading mechanism.
Upon such loading, the automatic loading mechanism makes use of a transporting force of paper transport tractors provided forwardly and backwardly of a transfer region (printing process station mentioned above) to transport the continuous paper to pass through the transfer region and then through a fixing station to a stacker under the guidance of transfer guides and other guide members. The continuous paper has feed holes formed successively in an equally separated relationship from each other along the opposite sides thereof for engaging with the paper transport tractors of the continuous paper printer so that the continuous paper may be transported by the paper transport tractors.
Upon printing, the photosensitive drum is rotated in a predetermined direction and the surface thereof is charged uniformly by the precharger. Then, the surface of the photosensitive drum is exposed to light by the exposure unit to form an electrostatic latent image of a pattern corresponding to printing information from a host apparatus on the surface of the photosensitive drum. The electrostatic latent image is developed into a toner image by the development unit.
Meanwhile, the continuous paper is transported from a hopper to a transfer position under the guidance of various guides by a paper transport mechanism such as a tractor. At the transfer position, the toner image on the photosensitive drum is transferred to the continuous paper by the transfer charger disposed in an opposing relationship to the photosensitive drum across the continuous paper.
Thereafter, the toner image transferred to the continuous paper is fixed to the continuous paper by heat, a pressure or light applied thereto by the fixing station, and is then sent out to the stacker or else is subject to post-processing by a post-processing apparatus such as a cutter apparatus.
The surface of the photosensitive drum after the transfer step has toner powder remaining thereon without having been transferred to the continuous paper, and the remaining toner powder must be removed from the photosensitive drum. Therefore, the charge of the remaining toner powder is removed by the AC discharger, and then the remaining toner powder is removed mechanically from the surface of the photosensitive drum by the cleaning unit. Usually, a cleaning blade or a cleaning brush is frequently used as the mechanical removing means.
After the remaining toner powder is removed from the photosensitive drum in this manner, optical discharge is performed by the LED discharge in order to return the potential on the surface of the photosensitive drum to its initial state (0 V). Then, in preparation for the next transfer step, the surface of the photosensitive drum is charged uniformly by the precharger again.
In a printer which prints on continuous paper as described above, the continuous paper after printed is either taken up onto and accommodated as a roll, or folded and accommodated in a stacker.
Continuous paper used for the latter case has portions called perforations formed at fixed intervals therein so that the continuous paper may be folded at the perforations thereof. In this instance, in order to fold and accommodate the continuous paper with certainty into the stacker, when the continuous paper is set to the continuous paper printer, a fold position (perforation position) of the continuous paper must be arranged at a correct position in accordance with the folding length of the continuous paper, that is, in accordance with the distance between adjacent perforations. It is to be noted that, in the present specification, the term "perforation" is used to signify a large number of very small holes perforated in a continuous printing medium in a row or line perpendicular to the longitudinal direction of the continuous printing medium (in which the continuous printing medium is transported) in order to facilitate folding of the continuous printing medium along the line(refer to perforation 1c in any of FIGS. 13 to 16 and 22).
In order to perform such positioning of a perforation, a continuous paper setting section (continuous medium mounting section) of a continuous paper printer is conventionally constructed in such a manner as shown in FIG. 22.
In particular, a tractor mechanism (paper transport tractor) 73 for a continuous paper printer is constructed such that continuous paper 1 is set into it while it is held by a pair of paper holders 731 and 732 from the opposite sides thereof. Each of the paper holders 731 and 732 has graduations (stickers) 351 provided thereon each of which indicates a position at which the continuous paper 1 is to be set as an arrangement position for a perforation 1c. The graduations 351 of the two paper holders 731 and 732 indicate the same positions as each other.
Each of the graduations 351 of the paper holder 731 has numerical value information (stickers) 361' provided therefor which indicates the distances (paper fold lengths) between adjacent perforations 1c of different continuous papers to be set to the positions of the graduations 351. It is to be noted that, in FIG. 22, each of the particular numerical values "9", "10", . . . , "14" provided for the graduations :351 represents the distance (unit: inch) between adjacent perforations 1c which is different depending upon the type of the continuous paper 1.
When an operator tries to set the continuous paper 1 to the printer, the operator recognizes the distance (paper fold length) between perforations 1c of the continuous paper 1 and sets the continuous paper 1 so that the position of one of the graduations 351 to which the numerical value information 361' corresponding to the distance is provided and the position of a perforation 1c may coincide with each other. In particular, in order to set the continuous paper 1 which has perforations 1c the distance between which is, for example, 10 inches, the position of a perforation 1c of the continuous paper 1 is brought into coincident with the position of that one of the graduations 351 to which "10" is added as the numerical value information 361'.
Conventionally, as a method of printing on both faces of continuous paper, a method is available wherein two such continuous paper printers (single-sided printers) as described above are connected to each other such that the front face (or back face) of the continuous paper is printed by the first one of the continuous paper printers first and then, after the continuous paper is twisted so as to be revered, the back face (or front face) of the continuous paper is printed by the second continuous paper printer.
However, since the method described above requires two continuous paper printers and further requires a mechanism for reversing continuous paper between the continuous paper printers, it has a subject to be solved in that not only the printing velocity is reduced, but also a very large installation area is required for the apparatus, and so forth.
Therefore, in recent years, a double-sided printer has been proposed wherein a pair of such printing process sections as described above are provided on the opposite sides of a paper transport path (continuous paper). According to a double-sided printer of the type just described, printing on the front face of continuous paper is performed by one of the printing process sections and printing on the back face of the continuous paper is performed by the other printing process section in the single apparatus. Accordingly, since the double-sided printer does not require reversal of continuous paper and does not require connection of two apparatus to each other, the problems regarding the printing velocity, installation area and so forth are eliminated.
However, the double-sided printer described above presents a new subject to be solved in regard to an automatic loading mechanism for automatically loading continuous paper.
In particular, in the double-sided printer described above, since the printing process sections (photosensitive drums and so forth) are present on the opposite sides of the paper transport path (continuous paper), it is very difficult in regard to the apparatus layout to dispose a tractor mechanism which exerts a transporting force to act upon the continuous paper between the printing process sections. Further, even if the tractor mechanism is disposed between the printing process sections, this increases the size of the apparatus.
Upon automatic mounting (automatic loading) of continuous paper, it is difficult to transport the continuous paper only by transporting force of the tractor mechanism on the upstream side with respect to the printing process sections so that a leading end portion of the continuous paper may pass between the two printing process sections and reach the tractor mechanism on the downstream side with certainty. Therefore, it is desired that, where a plurality of printing process sections are provided in a single printer, continuous paper can be transported to allow automatic loading thereof with certainty without additional provision of a new tractor mechanism or some other transport mechanism between the printing process sections.
Meanwhile, a single-sided printer which includes only one printing process section does not particularly suffer from a problem if the transporting direction of continuous paper is a horizontal direction. However, if the transporting direction of the continuous paper in the printing process section includes a vertical direction, then a leading end portion of the continuous paper may possibly be warped downwardly by the gravity, resulting in failure to effect automatic loading of the continuous paper. Therefore, also with regard to a single-sided printer, it is desired to allow continuous paper to be transported without additionally providing a new tractor mechanism or some other transporting mechanism so that automatic loading of the continuous paper can be performed with certainty irrespective of the transporting direction of the continuous paper.
On the other hand, when a continuous paper printer of the type wherein continuous paper after printed is folded and accommodated into a stacker performs automatic loading of continuous paper, as described hereinabove with reference to FIG. 22, an operator refers to the numerical value information 361' and the graduations 351 to set the continuous paper 1 to a position corresponding to the distance between perforations 1c of the continuous paper 1.
In this instance, where various types of continuous paper which are different in fold length (distance between perforations) are settable to the continuous paper printer, a large number of graduations 351 and numerical value information 361' must be provided, and depending upon a case, the indications of the graduations 351 and/or the numerical value information 361' are complicated such that the graduations 351 or the numerical values of the numerical value information 361' are indicated closely to each other or the graduations 351 for a plurality of types of continuous paper of different sizes are indicated in an overlapping relationship with each other (where paper sizes have a common multiple).
Further, the double-sided printer described above is used switchably in a mode wherein the two printing process sections are used to perform double-sided printing and another mode wherein only one of the printing process sections is used to perform single-sided printing. In this instance, since the transport path length of the continuous paper 1 is somewhat different whether the double-sided print is used in the double-sided printing mode and the single-sided printing mode, even for the continuous paper 1 of the same fold length (distance between perforations), the continuous paper setting position must be varied between the double-sided printing mode and the single-sided printing mode. Accordingly, where a double-sided printer is provided with such graduations 351 and numerical value information 361' as shown in FIG. 22, the graduations 351 and the numerical value information 361' must be provided for each of the different types of the continuous paper 1 and for each printing mode. This further complicates the indications of the graduations 351 and numerical value information 361'.
Further, upon setting of the continuous paper 1, conventionally an operator discriminates and determines one of the graduations 351 to which a perforation 1c of the continuous paper 1 should be set based on the printing mode and the fold length (distance between perforations). Therefore, in a printer of the type which has a plurality of printing modes and to which various kinds of continuous papers having different fold lengths (distances between perforations) can be set, an operator is liable to make an error in setting the continuous paper 1, and such erroneous setting gives rise to such troubles as paper jamming, wrong position printing, irregular paper stacking in a stacker and so forth.